Subject: [PATCH 2/3] powerpx/xive: Fix irq target selection returning out of bounds cpu#

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 10 Apr 2017 16:23:20 +1000

xive_pick_irq_target() first tries to construct a mask that is
the intersection of the requested affinity, online CPUs, and
the group of CPUs that are on the same chip as the interrupt
source.

If that resulting mask is empty, we were incorrectly returning
nr_cpu_ids as a target.

Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
---
 arch/powerpc/sysdev/xive/common.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
index dbbe446..abda9b2 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -492,7 +492,7 @@ static int xive_pick_irq_target(struct irq_data *d,
 
 	/*
 	 * If we have chip IDs, first we try to build a mask of
-	 * CPUs matching ther CPU and find a target in there
+	 * CPUs matching the CPU and find a target in there
 	 */
 	if (xd->src_chip != XIVE_INVALID_CHIP_ID &&
 		zalloc_cpumask_var(&mask, GFP_ATOMIC)) {
@@ -503,7 +503,9 @@ static int xive_pick_irq_target(struct irq_data *d,
 				cpumask_set_cpu(cpu, mask);
 		}
 		/* Try to find a target */
-		if (!cpumask_empty(mask))
+		if (cpumask_empty(mask))
+			cpu = -1;
+		else
 			cpu = xive_find_target_in_mask(mask, fuzz++);
 		free_cpumask_var(mask);
 		if (cpu >= 0)
-- 
2.9.3